Faster way to find out if a user exists on a system?

问题:

I have an application that checks to see if a user exists (if not create it) every time it starts. This is done as follows:

bool bUserExists = false; DirectoryEntry dirEntryLocalMachine =      new DirectoryEntry("WinNT://" + Environment.MachineName + ",computer");  DirectoryEntries dirEntries = dirEntryLocalMachine.Children;  foreach (DirectoryEntry dirEntryUser in dirEntries) {     bUserExists = dirEntryUser.Name.Equals("UserName",          StringComparison.CurrentCultureIgnoreCase);      if (bUserExists)       break; } 

The problem is on the majority of the systems where it is deployed. This can take 6 - 10 seconds, which is too long ... I need to find a way to reduce this (as much as possible). Is there a better or faster way I can use to verify if a user exists on the system or not?

I know there are other ways to solve this, like have the other applications sleep for 10 seconds, or have this tool send a message when it is ready, etc... But if I can greatly reduce the time it takes to find the user, it would make my life much easier.

回答1:

.NET 3.5 supports new AD querying classes under the System.DirectoryServices.AccountManagement namespace.

To make use of it, you'll need to add "System.DirectoryServices.AccountManagement" as a reference AND add the using statement.

using System.DirectoryServices.AccountManagement;   using (PrincipalContext pc = new PrincipalContext(ContextType.Machine)) {     UserPrincipal up = UserPrincipal.FindByIdentity(         pc,         IdentityType.SamAccountName,         "UserName");      bool UserExists = (up != null); } 

For versions of .NET prior to 3.5, here is a clean example I found on dotnet-snippets

DirectoryEntry dirEntryLocalMachine =     new DirectoryEntry("WinNT://" + Environment.MachineName + ",computer");  bool UserExists =     dirEntryLocalMachine.Children.Find(userIdentity, "user") != null; 

回答2:

You want to use the DirectorySearcher.

Something like this:

static bool userexists( string strUserName ) {     string adsPath = string.Format( @"WinNT://{0}", System.Environment.MachineName );     using( DirectoryEntry de = new DirectoryEntry( adsPath ) ) {         try {             return de.Children.Find( strUserName ) != null;         } catch( Exception e ) {             return false;         }     } } 

That should be quicker. Also, you can reduce the properties if all you are doing is checking for existence.

回答3:

The following in a command prompt returns 1 if 'username' exists.

net user | find "username" /c

回答4:

This should do it (when you can't use System.DirectoryServices.AccountManagement):

static bool userExists(string sUser) {     using (var oUser = new DirectoryEntry("WinNT://" + Environment.MachineName + "/" + sUser + ",user"))      {          return (oUser != null);     } } 

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